K.T. McFarland came into the White House as a deputy to Trump's first national security adviser, Michael Flynn.
It was in 2010 that she held a regular presence on air as a Fox News Channel analyst on matters of national security, and was highly critical of President Obama's methods in combatting terrorism.
McFarland's expected departure will likely elevate the status of Dina Powell, who is deputy national security adviser for strategy.
The shakeup also decreased homeland security adviser Tom Bossert's power within the council.
As noted by CNN, McFarland's position as the top deputy national security adviser had been "tenuous" for a while. He was eventually pressured to resign and has since been replaced by Lt. Gen. H.R. McMaster. McMaster immediately expressed a desire to run a less hierarchical organization and be more accessible to his staff.
The officials described McFarland's move as a promotion because Singapore is a key USA ally.
Philippines struck by 5.7 magnitude natural disaster
Phivolcs said Intensity 7 was felt in Mabini, Batangas while Intensity 6 was felt in Calatagan, Nasugbu and Tingloy in Batangas . A Reuters reporter felt a tremor for over a minute in the Makati business district of Manila .
McFarland is expected to remain at her post for the next two weeks before President Trump formally submits her as a nominee for the ambassadorship. She previously worked as an aide in the Richard Nixon and Gerald Ford administrations, and she served as a Pentagon speechwriter and spokesman under President Ronald Reagan.
Donald Trump's National Security Council has even fewer familiar faces following the third forced resignation in less than four months.
McFarland's style had grated against some of the professional staff members on the National Security Council, which sees itself as apolitical.
The NSC section of the White House website is blank, saying: "Check back soon for more information". The New York Times last month identified two NSC officials as having helped House intelligence committee Chairman Devin Nunes view secret reports that showed Trump and his associates were incidentally swept up in foreign surveillance by USA intelligence agencies.
Police said the 39-year-old suspect had been ordered to leave Sweden in December because his request for a residence permit was rejected.